Generate hash from chunked file
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I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
asked Nov 19 at 10:14
Enrique de Miguel
13319
add a comment |
up vote
0
down vote
favorite
I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
asked Nov 19 at 10:14
Enrique de Miguel
13319
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
Nov 19 at 12:26
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I haveMessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();
– Enrique de Miguel
Nov 19 at 12:52
1
The MessageDigest objects retains all the necessary state. That's why there's anupdate()method.
– James K Polk
Nov 19 at 16:41
It's a web service that receives file chunks of the same file in different requests. This means that I have to maintain the state ofMessageDigest shain a safe way between requests until I can dobyte hash = sha.digest();
– Enrique de Miguel
Nov 22 at 8:36
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
asked Nov 19 at 10:14
Enrique de Miguel
13319
I'm programming a web service for uploading long files. The client sends the chunks whenever it wants. I need to calculate the hash of this file while theese chunks are received.
I've seen that you can do somenthing like this:
byte buf = new byte[8192];
MessageDigest sha = MessageDigest.getInstance("SHA1");
FileInputStream inp = new FileInputStream(new File("D:\season4_mlp.rar"));
int n;
while((n = inp.read(buf)) > 0)
sha.update(buf, 0, n);
byte hash = sha.digest();
The problem is that I need to do this with different chunks of the same file and I don't know when they are going to come. I would need to keep the state of this hash calculation.
java hash cryptography bouncycastle message-digest
java hash cryptography bouncycastle message-digest
asked Nov 19 at 10:14
Enrique de Miguel
13319
asked Nov 19 at 10:14
Enrique de Miguel
13319
edited Nov 19 at 13:35
asked Nov 19 at 10:14
Enrique de Miguel
13319
asked Nov 19 at 10:14
Enrique de Miguel
13319
asked Nov 19 at 10:14
Enrique de Miguel
13319
13319
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
Nov 19 at 12:26
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I haveMessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();
– Enrique de Miguel
Nov 19 at 12:52
1
The MessageDigest objects retains all the necessary state. That's why there's anupdate()method.
– James K Polk
Nov 19 at 16:41
It's a web service that receives file chunks of the same file in different requests. This means that I have to maintain the state ofMessageDigest shain a safe way between requests until I can dobyte hash = sha.digest();
– Enrique de Miguel
Nov 22 at 8:36
add a comment |
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
Nov 19 at 12:26
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I haveMessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();
– Enrique de Miguel
Nov 19 at 12:52
1
The MessageDigest objects retains all the necessary state. That's why there's anupdate()method.
– James K Polk
Nov 19 at 16:41
It's a web service that receives file chunks of the same file in different requests. This means that I have to maintain the state ofMessageDigest shain a safe way between requests until I can dobyte hash = sha.digest();
– Enrique de Miguel
Nov 22 at 8:36
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
Nov 19 at 12:26
The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
Nov 19 at 12:26
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I have
MessageDigest sha that it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state of MessageDigest sha until I have all the data and then I can do byte hash = sha.digest();– Enrique de Miguel
Nov 19 at 12:52
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I have
MessageDigest sha that it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state of MessageDigest sha until I have all the data and then I can do byte hash = sha.digest();– Enrique de Miguel
Nov 19 at 12:52
1
1
The MessageDigest objects retains all the necessary state. That's why there's an
update() method.– James K Polk
Nov 19 at 16:41
The MessageDigest objects retains all the necessary state. That's why there's an
update() method.– James K Polk
Nov 19 at 16:41
It's a web service that receives file chunks of the same file in different requests. This means that I have to maintain the state of
MessageDigest sha in a safe way between requests until I can do byte hash = sha.digest();– Enrique de Miguel
Nov 22 at 8:36
It's a web service that receives file chunks of the same file in different requests. This means that I have to maintain the state of
MessageDigest sha in a safe way between requests until I can do byte hash = sha.digest();– Enrique de Miguel
Nov 22 at 8:36
add a comment |
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The code you posted doesn't require BouncyCastle, and unless you've jiggered your provider list doesn't use it at all. But if you mean you want to hash the data chunks out of order, you can't do that, not with JCE nor with BC LWAPI, because that's altering the data which is exactly what any decent crypto-hash and even SHA1 is designed to prevent.
– dave_thompson_085
Nov 19 at 12:26
I will work the hash out using the chunks in order. The question it's been edited for better undestanding... In the example I have
MessageDigest shathat it's used to generate the final hash. The point is that there is a gap between one chunk and the next one and so I have to keep the state ofMessageDigest shauntil I have all the data and then I can dobyte hash = sha.digest();– Enrique de Miguel
Nov 19 at 12:52
1
The MessageDigest objects retains all the necessary state. That's why there's an
update()method.– James K Polk
Nov 19 at 16:41
It's a web service that receives file chunks of the same file in different requests. This means that I have to maintain the state of
MessageDigest shain a safe way between requests until I can dobyte hash = sha.digest();– Enrique de Miguel
Nov 22 at 8:36